Soviet Occupation of Denmark 1945
My understanding is that Blumentritt "aided" the British advance by not strongly resisting the allies once across the Elbe at Lauernburg on May 1st and that he had established contact with Montgomery before the arrival of the main German surrender delegation at Luneburg Heath.
I suppose that had a more hardline German commander been in place, the British could have been delayed crossing the Elbe (a crossing resisted by the Luftwaffe and SS troops) allowing the Russians to sweep along the Baltic coast. The British would have been further held by the chaos of the retreat of the Germans facing the Red Army.
Let's suppose the Russians reach the Danish border on May 3rd or 4th. It's likely German troops would have resisted not least to defend ports where refugees from the Baltic were arriving.
I don't know what the Swedes could or would have done. They didn't intervene in Norway when the Russians entered from the north - why and on what basis would they have crossed over to Copenhagen ?
Steffan, whose expertise I bow to in these matters, makes valid points about the nature of the resistance. Would the Soviet commander have respected or dealt with a Danish provisional Government such as occurred in OTL ? it seems improbable as Aksel Larsen was hardly a Moscow man compared with the German communists sent to Berlin in the wake of the Red Army.
The Russians would have had to deal with the resistance and the indigenous Danish political leader so perhaps Larsen and communist supporters take key positions in a Social Democrat-led Government. It seems improbable that the Red Army could have forced a maerger between the Social Democrats and Communists such as happened in the Russian sector of Germany in 1946.
Given the huge strategic importance of the Kattegat and Skaggerak, I can't see the Soviets just walking away without something. One possibility I suppose is the "Finland"-type solution with Denmark completely neutral. This might be as part of a Nordic neutrality solution in which both Washington and Moscow agree to the neutrality of Norway, Denmark and Finland - this would be advantageous to the Russians in terms of access to and from the Barents Sea and the Baltic.
Politically, in OTL, the Communists won 18 seats on 12.5% of the vote in the October 1945 election bur declined soon after. It might be different in a Denmark more under Soviet influence. The Communists, as part of the Left bloc, could retain a presence in Government for some time.
I don't subscribe to the Greece scenario - it didn't happen in Austria for example though attitudes to the Russians would be different if they indulged in some of the excesses seen in Germany. That might well happen of course.